In packaging machines, such as packaging machines employed to package snack foods, strip bag material is delivered to a former which configures the strip bag material into a tubular configuration. The tubular bag material is longitudinally sealed adjacent its longitudinal edges so that it maintains a tubular configuration, with product being delivered to the interior of the tubular bag material through the former. The tubular bag material is subsequently engaged by sealing jaws that transversely seal the tubular bag material and transversely cut the tubular bag material so that discrete bags of product are provided. The tubular bag material is moved through this apparatus by belts or rollers to which a vacuum is applied. Apertures in the belts or rollers are positioned against the tubular bag material so that the tubular bag material is urged into contact therewith due to the reduced air pressure applied to the surfaces of the tubular bag material engaged by the belt or rollers.
Examples of the above-described packaging apparatus are described in U.S. Pat. Nos. 4,753,336 and 4,663,917, while a previous assembly to drive the tubular bag material through the packaging machine is described in U.S. Pat. No. 4,910,943.
Typically two or three belts are provided to drive the bag material. In some instances two of the belts are located adjacent each other so that the longitudinal edges of the tubular bag material are positioned therebetween, with the overlapping edges being engaged by a backseal bar assembly that heats the tubular bag material to longitudinally seal the bag material. Typically, an inner support is located in the interior of the tubular bag material and against which the tubular bag material is pressed by the backseal bar assembly. The belts are driven and are supported by rollers that have a rotational axis that is generally horizontal, with the tubular bag material having a longitudinal axis that is generally vertical. Each belt has an engaging length that engages the tubular bag material, with the engaging lengths being generally planar and located in the same plane. The tubular bag material is also engaged by a third belt located on the opposite side of the tubular bag material to the backseal bar and again is driven.
In other instances only two belts are used, the belts being located on opposite sides of the bag material.
The above-described belt arrangements have the disadvantage that they change the configuration of the tubular bag material to the extent that it reduces the area available for the product to move when being delivered to the interior of the tubular bag material. Accordingly, movement of the product is inhibited.